Drainage basin is a geographic term about rivers. It is also called catchment, catchment area, catchment basin, drainage area, river basin, and water basin.^[1]

It is an area of land. All water that falls on that land flows into one river. It can flow directly into the river or go through tributaries (smaller rivers that flow into the bigger river) first.

One river can drain a large area. For example, more than half of the United States is drained by the Mississippi and its tributaries. The Amazon basin is similarly large.

River basins are an open system with inputs and, outputs. Water comes in as precipitation and goes out as discharge.

This term watershed can have two main meanings:

• Meaning drainage divide, the line that separates neighbouring drainage basins
• Meaning drainage basin in North American usage. (an area of land where surface water converges)

There are also a number of figurative meanings as a metaphor.

• Basin (geology)
• Endorheic basin
• River system

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